1. Field of the Invention
The present invention relates to a yaw rate sensor failure diagnosing device for judging abnormality (or failure) of a yaw rate sensor with precision.
2. Description of Related Art
Various vehicle behavior control operations such as automatic braking control, driving force distributing control, etc. have been recently carried out on vehicles in order to enhance driveability and turning performance. In these control operations, a yaw rate sensor for detecting a yaw rate is mounted in order to know the present behavior of the vehicle. Therefore, when abnormality occurs in the yaw rate sensor, the vehicle behavior control itself is abnormal, and thus it has been desired to establish failure diagnosis for yaw rate sensors.
For example, Japanese unexamined Patent publication JP-A-2003-104139 discloses a technique of carrying out such a sensor failure diagnosis. According to this technique, with respect to sensor values detected when a vehicle is in a vehicle motion state that the sensor value is equal to a zero point and when the vehicle is in a vehicle motion state that the sensor value is equal to a preset reference value, the displacement of the sensor value from the zero point or the reference value is observed, and it is judged on this observation whether the sensor is abnormal or not.
In the failure diagnosis disclosed in the above publication, however, it is possible to judge abnormality only in the vehicle motion state that the sensor value is equal to the zero point or the preset reference value, and thus it is impossible to judge abnormality by detecting continuously ever-changing parameters. Accordingly, there is a problem that it is difficult to judge abnormality for a long time in some vehicle travel states and thus the abnormality judgment is remarkably late.
Particularly with respect to a control operation using a yaw rate sensor, for example, a vehicle behavior control operation of controlling braking force to induce a yaw moment to the vehicle, the output from the yaw rate sensor is directly connected to the control value, and thus it is required to detect an accurate value on a real-time basis even though the vehicle is in any vehicle motion state. Accordingly, when abnormality occurs in the yaw rate sensor, it is required to immediately detect abnormality and correct the control even though the vehicle is in any vehicle motion state.